In the present study, Inhibitory effects of the ethanol extract of Saussurea lappa (S. lappa) on the growth, acid production, adhesion and water-insoluble glucan synthesis of Streptouccus mutans (S. mutans) were examined. The growth and acid production of S. mutans were Inhibited by the presence of ethanol extract of S. lappa (0.5-4 mg/ml) significantly. The ethanol extract of S. lappa (0.25-4 mg/ml) also significantly lowered the adherence of S. mutans in a dose dependent manner. In water-insoluble glucan synthesis assay, 2-4 mg/ml of the ethanol extract of S. lappa significantly inhibited the formation of water-insoluble glucan. These results suggest that S. lappa may inhibit the caries-inducing properties of S. mutans. Further studies are necessary to clarify the active constituents of S. lappa responsible for such biomolecular activities.